Proposal for hybrid passive cooling system of batteries In the electric car.
3rd International Conference on Engineering and ICT (ICEI2012)
Melaka, Malaysia
4 – 6 April 2012
PROPOSAL FOR HYBRID PASSIVE COOLING SYSTEM OF BATTERIES
IN THE ELECTRIC CAR
N.Tamaldin1,a* and M.F.Abdollah2,b
1,2
Faculty of Mechanical Engineering, Universiti Teknikal Malaysia Melaka,
Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, MALAYSIA
a
Email: noreffendy@utem.edu.my, bEmail: mohdfadzli@utem.edu.my
Abstract—This paper addresses the challenges faced by Electric
Vehicle (EV) thermal management system and proposed a
method to overcome them. Due to the non existence of internal
combustion engine (ICE) in EV, the driving mechanisms of
conventional cooling system need to be revamped. Therefore, in
this paper a combination of liquid cooled, air cooled and phase
change material (PCM) cooling system was introduced. The
main heat dissipation from EV was identified coming from
electric motor, battery module and the electronics controller and
components. As this is a preliminary study, the reliability and
sustainability of the system need to be further investigated. The
investigation would include the, simulation and modeling of
heat dissipated from the EV and also the cooling capacity of the
proposed cooling system.
Keywords — EV Thermal Managemet, Passive Cooling,
Phase Change Material, EV cooling system.
I.
INTRODUCTION
Driven by persistent concerns about the global
environment, petroleum supplies and prices, interest in
advanced and alternative vehicle power train technologies
continues grow. Electric vehicles (EVs) are an effective
technology for reducing the overall amount of petroleum
consumed for transportation.
An EV is propelled by electric motor(s), using
electrical energy stored in batteries. EVs operate with a
very simple architecture: a battery, charged from an
external source, supplies electricity to one or more motors
that drive the wheels. Because the torque generated by an
electric motor is independent of speed, EVs can operate
without gear shifting, and it is often advantageous to
connect individual motors directly to the wheels.
Furthermore, energy can be recovered during braking by
having the motors act as generators and charging the
battery. 2010 saw the launch of the first modern EV from
a major manufacturer: the Nissan Leaf [1]. It is advertised
with a top speed of 145 km/hour and a range of 117 km;
adequate for urban driving, but the limited battery
capacity and lengthy recharging make it impractical for
long journeys.
Effective energy utilization is very important in EVs.
Therefore, every component in the EVs should operate at
the most ideal condition. In order to achieve the ideal
operating temperature for these components, efficient
thermal management is essential. The purpose of a
thermal management system is to deliver optimum power
to EV. An ideal thermal management system should be
able to maintain the desired uniform temperature by
removing the same amount of heat generated by the
sources.
In EV, the three major components that produce heat
are battery, controller and motor. However, the battery
pack is a key component of their fuel savings potential,
and the battery is also one of the most expensive
components in the vehicle. Various battery chemistries
are being tested and promoted, of which NiMH and Liion are, so far, the most promising. The NiMH is the
leading battery type for PHEVs since it is presently being
used in the HEV market [2]. On the other hand, Li-ion
batteries have higher energy densities but they require
thermal management solutions for this high-power
application. Temperature of the Li-ion battery has to be
regulated within the optimum window, failing of which
can adversely affect the electrochemical performance of
Li-ion cell charge acceptance, power and energy
capability, reliability, cycle life, safety and cost [3-5].
The operation of most Li-ion cell is limited to a
temperature of 20°C to 55°C. Abuse conditions, such as
an operation at high temperatures, steeply accelerate the
accumulation of thermal energy in Li-ion cells.
Generally air conditioning system cooling system is
preferred however showing reduction from 34% to 46%
of the vehicle range. Heating was also found to be a
threat to the vehicle range from 46% to 68% reduction
[8].
For battery cells of higher energy density and greater
heat generation, as found in EVs, it is probable that active
cooling systems with a liquid coolant will be required
[6]. However, using liquid as cooling agent means more
mass, has a potential for leaks, need more components,
and could cost more. Furthermore, maintenance and
repair of a liquid cooled pack is more involved and
costlier. In addition to the cost advantage, there is also a
reduction size and weight of the modules using air as
cooling paths.
More effective, simpler, and less expensive thermal
management would assist in the further development of
affordable battery packs and increase market penetration
of EVs. Therefore, the present paper proposed a new
concept of battery thermal management by using a hybrid
passive cooling system. Battery thermal management
using air and phase change material (PCM) for the Li-ion
battery pack has potential to bring benefits, such as
passively buffering against life-reducing high battery
operating temperatures.
II.
PROPOSED METHOD
Figure 1 shows a proposed schematic drawing of the
cooling system for the EV. As for the motor, air is
achieved by directing/blowing the outside air across the
3rd International Conference on Engineering and ICT (ICEI2012)
Melaka, Malaysia
4 – 6 April 2012
motor via radiator. Due to the fact that heat generated at
high speed would become a thread, liquid cooling system
is highly recommended for the electric motor.
Multiple air ducts is an easy way to make a direct
intake from in front of the car to the battery pack. This
will directly flow the outside air to the battery pack in
addition to the PCM. Possibly the straight duct thru
passenger compartment can reduce losses. A system fan
or original radiator fan can be used to assist airflow,
practically during charging time where the car remains
stationery. In addition, another fan will be placed near
battery compartment in order to assist the hot air draw
quickly.
Air inlet
Coolant
Passage
Radiator
III.
HEAT TRANSFER SIMULATION AND MODELLING
In developing the EV thermal management system, one
of the key area is the heat transfer and cooling capacity
modeling of its electric motor, battery module and the
electronics components. Three modes of heat transfer
considered in EV are conduction, convection and
radiation. By identifying the sources of these modes of
heat transfer would greatly help to reduce them. An
example of hybrid electric vehicle model was use to
illustrated the sources of heat transfer as shown in figure
2. In the EV thermal management modeling, the heat
transfer from ICE was eliminated.
Front end
Fan
Motor
provides a low-resistance heat path for effective heat
transfer to the salt hydrates. The salt hydrates absorb
thermal energy through both the sensible heat and the
latent heat of phase change. The battery cells are inserted
into the PCM/graphite matrix structure as shown.
Gearbox
Figure 2. Sources of heat transfer considered [8]
Various thermal predictions was anticipated in order to improve the
thermal behavior of the electric motor, battery and electronics
component. Each of these components has to meet various thermal
conditions for optimization of the operating range. The thermal analysis
proposed include the prediction of various design to their thermal
behavior. Example in figure 3 shows various air flow design impact to
its thermal analysis.
Battery pack PCM /
graphite matrix
Rear end
Air outlet
Figure 1 Schematic of the EV thermal management system
The graphite matrix filled with commercial PCM (salt
hydrates) will be prepared with Li-ion cells connected in
series and parallel configuration to meet the voltage and
current requirement of the module. The module will be
integrated with safety circuits to regulate cell voltage and
prevent over-charge. All of the strings in the module will
be connected with a safety circuit that was rated for a
required current and potential. The module design, shown
in Figure 2, has a porous graphite matrix, impregnated
with salt hydrates, that provides structure and heat
dissipation. The graphite matrix holds the salt hydrates
like a sponge would. The high-conductivity graphite also
Figure 3. Example of thermal analysis on the battery module [6]
Similar techniques would be applied in this paper with
the use of other thermal simulation package. It is
expected that the thermal simulation shown in figure 3
would be a baseline for comparison for our proposed
design in this paper.
3rd International Conference on Engineering and ICT (ICEI2012)
Melaka, Malaysia
4 – 6 April 2012
IV.
[5]
DISCUSSION
The use of active air and liquid cooling adds
considerable complexity and limits the full use of the
battery’s capacity. However, thermal management using
phase change material (PCM) eliminates to the need for
the additional cooling systems and improves the power
use. Battery packs can be maintained at an optimum
temperature with proper thermal management, which can
be optimized by integrating PCM in the battery. PCM is
capable of removing large quantities of heat due to its
high latent heat of fusion. In principle, during discharge
of the battery, the heat generated could be absorbed by
the PCM integrated in between the cells in the battery
module. It acts as a heat sink absorbing the heat generated
by the battery. When the temperature of the module
exceeds the melting point of the PCM (78oC), it starts to
melt and the high latent heat of the PCM prevents the
battery temperature from rising sharply. This method of
thermal management eliminates the need for any kind of
manifold, fans, or pumps, which are usually necessary in
existing conventional thermal management systems.
PCM/Graphite
matrix
Cell
Battery module
Figure 3 Conceptual schematic of a battery module with PCM/graphite
thermal management
V.
Conclusions
The study involving EV thermal management have
been aggressively explored by the automotive
manufacturer in order to be successfully commercialized.
The method proposed in this paper may contribute to the
development and optimization of the EV thermal
management system. The main objective in this
development is to have a balance of energy consumption
from the thermal management system to the energy
utilise to drive the EV. The predictive modelling
proposed in this paper could assist in designing a more
robust thermal management system for EV with a more
economical cost.
REFERENCES
[1]
[2]
[3]
[4]
http://www.nissanusa.com/ev/media/pdf/specs/FeaturesAndSpe
cs.pdf, (Accessed 25 January 2012).
M. Duvall, Batteries for Plug-In Hybrid Electric Vehicles, The
Seattle Electric Vehicle to Grid (V2G) Forum, 2005.
R. Venugopal, Characterization of thermal cut-off mechanism
in prismatic lithium ion batteries, Journal of Power Sources,
101 (2003) 231-237.
G. Ning, B. Haran, B.N. Popov, Capacity fade study of li-ion
batteries cycled at high discharge rates, Journal of Power
Sources, 117 (2003) 160-169.
[6]
[7]
[8]
[9]
A. Peseran, Battery Thermal models for hybrid vehicle
simulations, Journal of Power Sources, 110 (2002), 377-382.
A. Pesaran, S. Burch and M. Keyser, An approach for
designing thermal management systems for electric and hybrid
vehicle battery packs, Proceedings of the 4th Vehicle Thermal
Management Systems Conference and Exhibition, 1999, pp. 2427.
A. Peseran, Battery Thermal management in EV’s and HEV’s:
Issues and Solutions, Proceedings of First annual Advanced
Automobile Battery Conference, 2001.
J.Rugh, Integrated Vehicle Thermal Management Combining
Fluid Loops in Electric Drive Vehicles, U.S. Department of
Energy Annual Merit Review, 2011
J. Horne, Getting “the word” out to the HEV technician about
thermal
control,
International
Conference
Thermal
Management for Electric Vehicles/HEV, 27-29 June 2011
Darmstadt, Germany.
Melaka, Malaysia
4 – 6 April 2012
PROPOSAL FOR HYBRID PASSIVE COOLING SYSTEM OF BATTERIES
IN THE ELECTRIC CAR
N.Tamaldin1,a* and M.F.Abdollah2,b
1,2
Faculty of Mechanical Engineering, Universiti Teknikal Malaysia Melaka,
Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, MALAYSIA
a
Email: noreffendy@utem.edu.my, bEmail: mohdfadzli@utem.edu.my
Abstract—This paper addresses the challenges faced by Electric
Vehicle (EV) thermal management system and proposed a
method to overcome them. Due to the non existence of internal
combustion engine (ICE) in EV, the driving mechanisms of
conventional cooling system need to be revamped. Therefore, in
this paper a combination of liquid cooled, air cooled and phase
change material (PCM) cooling system was introduced. The
main heat dissipation from EV was identified coming from
electric motor, battery module and the electronics controller and
components. As this is a preliminary study, the reliability and
sustainability of the system need to be further investigated. The
investigation would include the, simulation and modeling of
heat dissipated from the EV and also the cooling capacity of the
proposed cooling system.
Keywords — EV Thermal Managemet, Passive Cooling,
Phase Change Material, EV cooling system.
I.
INTRODUCTION
Driven by persistent concerns about the global
environment, petroleum supplies and prices, interest in
advanced and alternative vehicle power train technologies
continues grow. Electric vehicles (EVs) are an effective
technology for reducing the overall amount of petroleum
consumed for transportation.
An EV is propelled by electric motor(s), using
electrical energy stored in batteries. EVs operate with a
very simple architecture: a battery, charged from an
external source, supplies electricity to one or more motors
that drive the wheels. Because the torque generated by an
electric motor is independent of speed, EVs can operate
without gear shifting, and it is often advantageous to
connect individual motors directly to the wheels.
Furthermore, energy can be recovered during braking by
having the motors act as generators and charging the
battery. 2010 saw the launch of the first modern EV from
a major manufacturer: the Nissan Leaf [1]. It is advertised
with a top speed of 145 km/hour and a range of 117 km;
adequate for urban driving, but the limited battery
capacity and lengthy recharging make it impractical for
long journeys.
Effective energy utilization is very important in EVs.
Therefore, every component in the EVs should operate at
the most ideal condition. In order to achieve the ideal
operating temperature for these components, efficient
thermal management is essential. The purpose of a
thermal management system is to deliver optimum power
to EV. An ideal thermal management system should be
able to maintain the desired uniform temperature by
removing the same amount of heat generated by the
sources.
In EV, the three major components that produce heat
are battery, controller and motor. However, the battery
pack is a key component of their fuel savings potential,
and the battery is also one of the most expensive
components in the vehicle. Various battery chemistries
are being tested and promoted, of which NiMH and Liion are, so far, the most promising. The NiMH is the
leading battery type for PHEVs since it is presently being
used in the HEV market [2]. On the other hand, Li-ion
batteries have higher energy densities but they require
thermal management solutions for this high-power
application. Temperature of the Li-ion battery has to be
regulated within the optimum window, failing of which
can adversely affect the electrochemical performance of
Li-ion cell charge acceptance, power and energy
capability, reliability, cycle life, safety and cost [3-5].
The operation of most Li-ion cell is limited to a
temperature of 20°C to 55°C. Abuse conditions, such as
an operation at high temperatures, steeply accelerate the
accumulation of thermal energy in Li-ion cells.
Generally air conditioning system cooling system is
preferred however showing reduction from 34% to 46%
of the vehicle range. Heating was also found to be a
threat to the vehicle range from 46% to 68% reduction
[8].
For battery cells of higher energy density and greater
heat generation, as found in EVs, it is probable that active
cooling systems with a liquid coolant will be required
[6]. However, using liquid as cooling agent means more
mass, has a potential for leaks, need more components,
and could cost more. Furthermore, maintenance and
repair of a liquid cooled pack is more involved and
costlier. In addition to the cost advantage, there is also a
reduction size and weight of the modules using air as
cooling paths.
More effective, simpler, and less expensive thermal
management would assist in the further development of
affordable battery packs and increase market penetration
of EVs. Therefore, the present paper proposed a new
concept of battery thermal management by using a hybrid
passive cooling system. Battery thermal management
using air and phase change material (PCM) for the Li-ion
battery pack has potential to bring benefits, such as
passively buffering against life-reducing high battery
operating temperatures.
II.
PROPOSED METHOD
Figure 1 shows a proposed schematic drawing of the
cooling system for the EV. As for the motor, air is
achieved by directing/blowing the outside air across the
3rd International Conference on Engineering and ICT (ICEI2012)
Melaka, Malaysia
4 – 6 April 2012
motor via radiator. Due to the fact that heat generated at
high speed would become a thread, liquid cooling system
is highly recommended for the electric motor.
Multiple air ducts is an easy way to make a direct
intake from in front of the car to the battery pack. This
will directly flow the outside air to the battery pack in
addition to the PCM. Possibly the straight duct thru
passenger compartment can reduce losses. A system fan
or original radiator fan can be used to assist airflow,
practically during charging time where the car remains
stationery. In addition, another fan will be placed near
battery compartment in order to assist the hot air draw
quickly.
Air inlet
Coolant
Passage
Radiator
III.
HEAT TRANSFER SIMULATION AND MODELLING
In developing the EV thermal management system, one
of the key area is the heat transfer and cooling capacity
modeling of its electric motor, battery module and the
electronics components. Three modes of heat transfer
considered in EV are conduction, convection and
radiation. By identifying the sources of these modes of
heat transfer would greatly help to reduce them. An
example of hybrid electric vehicle model was use to
illustrated the sources of heat transfer as shown in figure
2. In the EV thermal management modeling, the heat
transfer from ICE was eliminated.
Front end
Fan
Motor
provides a low-resistance heat path for effective heat
transfer to the salt hydrates. The salt hydrates absorb
thermal energy through both the sensible heat and the
latent heat of phase change. The battery cells are inserted
into the PCM/graphite matrix structure as shown.
Gearbox
Figure 2. Sources of heat transfer considered [8]
Various thermal predictions was anticipated in order to improve the
thermal behavior of the electric motor, battery and electronics
component. Each of these components has to meet various thermal
conditions for optimization of the operating range. The thermal analysis
proposed include the prediction of various design to their thermal
behavior. Example in figure 3 shows various air flow design impact to
its thermal analysis.
Battery pack PCM /
graphite matrix
Rear end
Air outlet
Figure 1 Schematic of the EV thermal management system
The graphite matrix filled with commercial PCM (salt
hydrates) will be prepared with Li-ion cells connected in
series and parallel configuration to meet the voltage and
current requirement of the module. The module will be
integrated with safety circuits to regulate cell voltage and
prevent over-charge. All of the strings in the module will
be connected with a safety circuit that was rated for a
required current and potential. The module design, shown
in Figure 2, has a porous graphite matrix, impregnated
with salt hydrates, that provides structure and heat
dissipation. The graphite matrix holds the salt hydrates
like a sponge would. The high-conductivity graphite also
Figure 3. Example of thermal analysis on the battery module [6]
Similar techniques would be applied in this paper with
the use of other thermal simulation package. It is
expected that the thermal simulation shown in figure 3
would be a baseline for comparison for our proposed
design in this paper.
3rd International Conference on Engineering and ICT (ICEI2012)
Melaka, Malaysia
4 – 6 April 2012
IV.
[5]
DISCUSSION
The use of active air and liquid cooling adds
considerable complexity and limits the full use of the
battery’s capacity. However, thermal management using
phase change material (PCM) eliminates to the need for
the additional cooling systems and improves the power
use. Battery packs can be maintained at an optimum
temperature with proper thermal management, which can
be optimized by integrating PCM in the battery. PCM is
capable of removing large quantities of heat due to its
high latent heat of fusion. In principle, during discharge
of the battery, the heat generated could be absorbed by
the PCM integrated in between the cells in the battery
module. It acts as a heat sink absorbing the heat generated
by the battery. When the temperature of the module
exceeds the melting point of the PCM (78oC), it starts to
melt and the high latent heat of the PCM prevents the
battery temperature from rising sharply. This method of
thermal management eliminates the need for any kind of
manifold, fans, or pumps, which are usually necessary in
existing conventional thermal management systems.
PCM/Graphite
matrix
Cell
Battery module
Figure 3 Conceptual schematic of a battery module with PCM/graphite
thermal management
V.
Conclusions
The study involving EV thermal management have
been aggressively explored by the automotive
manufacturer in order to be successfully commercialized.
The method proposed in this paper may contribute to the
development and optimization of the EV thermal
management system. The main objective in this
development is to have a balance of energy consumption
from the thermal management system to the energy
utilise to drive the EV. The predictive modelling
proposed in this paper could assist in designing a more
robust thermal management system for EV with a more
economical cost.
REFERENCES
[1]
[2]
[3]
[4]
http://www.nissanusa.com/ev/media/pdf/specs/FeaturesAndSpe
cs.pdf, (Accessed 25 January 2012).
M. Duvall, Batteries for Plug-In Hybrid Electric Vehicles, The
Seattle Electric Vehicle to Grid (V2G) Forum, 2005.
R. Venugopal, Characterization of thermal cut-off mechanism
in prismatic lithium ion batteries, Journal of Power Sources,
101 (2003) 231-237.
G. Ning, B. Haran, B.N. Popov, Capacity fade study of li-ion
batteries cycled at high discharge rates, Journal of Power
Sources, 117 (2003) 160-169.
[6]
[7]
[8]
[9]
A. Peseran, Battery Thermal models for hybrid vehicle
simulations, Journal of Power Sources, 110 (2002), 377-382.
A. Pesaran, S. Burch and M. Keyser, An approach for
designing thermal management systems for electric and hybrid
vehicle battery packs, Proceedings of the 4th Vehicle Thermal
Management Systems Conference and Exhibition, 1999, pp. 2427.
A. Peseran, Battery Thermal management in EV’s and HEV’s:
Issues and Solutions, Proceedings of First annual Advanced
Automobile Battery Conference, 2001.
J.Rugh, Integrated Vehicle Thermal Management Combining
Fluid Loops in Electric Drive Vehicles, U.S. Department of
Energy Annual Merit Review, 2011
J. Horne, Getting “the word” out to the HEV technician about
thermal
control,
International
Conference
Thermal
Management for Electric Vehicles/HEV, 27-29 June 2011
Darmstadt, Germany.